In recent years, in the field of compact digital cameras, as the density of pixels of an image sensor increases, there are cases in which a sense of resolution deteriorates due to the influence of a small aperture blur.
In this regard, employment of a neutral density (ND) filter (variable-transmittance ND filter) that implements a desired transmittance without an aperture being changed by an applied voltage has been studied. Among ND filters, for example, a liquid crystal ND filter is used to reduce a drastic change in exposure and thus reduce an observer's fatigue by changing a transmittance when a light quantity drastically changes in an eyepiece image at the time of switching of an objective lens (see Patent Literature 1).